JP2009251085A - Wet developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wet developer, in which chargeability of toner particles can be controlled while assuring storage stability and fixability. <P>SOLUTION: The wet developer is prepared by dispersing toner particles comprising at least a colorant and a binder resin in a nonvolatile carrier liquid by using a polymer dispersant. The polymer dispersant has a pyrrolidone group; and the carrier liquid contains a metal soap expressed by general formula (RCOO)<SB>2</SB>M, wherein R represents a substituted or unsubstituted alkyl group, alkenyl group, aralkyl group or aryl group and M represents a divalent metal. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wet developer used in an image forming apparatus using a wet electrophotographic system such as a copying machine, a printer, a digital printing machine, etc.

  In electrophotographic image formation, generally, an electrostatic latent image is formed on an electrostatic latent image carrier such as a photoconductor by image exposure according to a document image or image data. The electrostatic latent image is developed into a visible toner image, and the toner image is transferred and fixed on a recording material to obtain a target image.

  Development methods can be divided into dry development methods and wet development methods. In the dry development method, a toner or a toner added with a carrier having magnetism or the like is used as a developer. The dry toner usually uses a pigment and a binder resin as main components, and a charge control agent, a conductivity control agent, a plasticizer, a release agent and the like are added or added as necessary. On the other hand, in the wet development method, a liquid developer in which toner particles mainly composed of a pigment and a binder resin, a charge control agent, a dispersion stabilizer and the like are dispersed in an electrically insulating dispersion medium (carrier liquid) is used. ing. The toner particles used in the wet developer can be made fine because there is no fear of escaping into the atmosphere, and those having an average particle size of submicron are also practical. Therefore, there are advantages such that an image having high resolution can be obtained and the toner image can be easily fixed.

In the wet development method, development is performed by electrostatically adhering charged toner particles to the electrostatic latent image on the electrostatic latent image carrier. In order to control the chargeability of toner particles, conventionally, a method of adding a charge adjusting agent such as a metal soap or a fatty acid is known. (For example, patent document 1).
Special table 2007-505953 gazette

  However, if it is attempted to control the chargeability of toner particles using only the charge control agent, the amount of charge control agent added increases and the fixability decreases. On the other hand, the dispersant is added in order to ensure the storage stability of the developer. However, when the addition amount is increased, the charge amount of the toner particles is increased. Therefore, it is possible to control the chargeability of the toner particles by changing the addition amount of the dispersant. However, when the dispersant is added excessively, the carrier liquid is easily held in the toner particles, and there is a problem that the fixing property is lowered. Further, when the charge amount is increased, toner particles are firmly attached to a toner carrier such as a photoconductor, so that there is a problem that the cleaning performance with respect to the toner carrier is lowered and the residual toner is increased even after cleaning. . Therefore, it is difficult to adjust the chargeability of the toner particles while ensuring storage stability and fixability.

  Accordingly, an object of the present invention is to provide a wet developer capable of adjusting the chargeability of toner particles while solving the above-described problems and ensuring storage stability and fixability.

In order to solve the above problems, the wet developer of the present invention is a wet developer obtained by dispersing toner particles composed of at least a colorant and a binder resin in a non-volatile carrier liquid using a polymer dispersant. The polymer dispersant has a pyrrolidone group, the carrier liquid has the general formula (RCOO) ₂ M (R represents a substituted or unsubstituted alkyl group, alkenyl group, aralkyl group or aryl group, and M represents a divalent group. The metal soap represented by this is included.

  In this invention, the metal salt of a C5-C15 fatty acid can be used for the said metal soap.

  A polyester resin having an acid value of 20 mgKOH / g or more can be used for the binder resin.

According to the present invention, a polymer dispersant having a pyrrolidone group is used, and a general formula (RCOO) ₂ M (R represents a substituted or unsubstituted alkyl group, alkenyl group, aralkyl group or aryl group as a charge control agent. , M represents a divalent metal)), the chargeability of the toner particles can be adjusted while ensuring storage stability and fixability. It is considered that the polymer dispersant having a pyrrolidone group can ensure storage stability even when added in a small amount, and that the metal soap can adjust the chargeability of the toner particles without affecting the fixability.

Hereinafter, embodiments of the present invention will be described in detail.
The wet developer of the present invention is a wet developer in which toner particles comprising at least a colorant and a binder resin are dispersed in a non-volatile carrier liquid using a polymer dispersant, and the polymer dispersant is pyrrolidone. And the carrier liquid contains a metal soap represented by the general formula (RCOO) ₂ M (R represents an alkyl group, M represents a divalent metal).

The wet developer according to the present invention contains at least a carrier liquid, toner particles, and a polymer dispersant.
(Carrier liquid)
As the carrier liquid, a non-volatile solvent having a high dielectric constant with a dielectric constant of 3 or less can be used. For example, liquid paraffin, silicon oil, animal and vegetable oils, mineral oil, and the like can be used from the viewpoint of odor, pollution-free property, and cost, but liquid paraffin is preferable. In the present invention, the non-volatile solvent is a solvent having a flash point of 70 ° C. or higher unless otherwise specified.

(Toner particles)
The toner particles used in the present invention contain at least a colorant and a binder resin.
The binder resin is a thermoplastic resin and is not particularly limited as long as it does not substantially dissolve in the carrier liquid. A polyester resin is particularly preferable. The polyester resin has sharp melt properties, and it is possible to achieve both storage stability and fixability.

  Specifically, the polyester resin means a resin obtained by polycondensation of a polybasic acid and a polyhydric alcohol. As polybasic acids, isophthalic acid, terephthalic acid, malonic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, itaconic acid and its acid anhydride, trimellitic acid, trimesic acid, pyromellitic An acid etc. can be mentioned. Isophthalic acid, terephthalic acid, and trimellitic acid are preferable.

  As the polyhydric alcohol, the polyhydric alcohol is not limited to these, but propylene glycol such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, dipropylene glycol, 1,4- Butanediols such as butanediol, neopentyl glycol, alkylene glycols (aliphatic glycols) such as 1,6-hexanediol and their alkylene oxide adducts, bisphenols such as bisphenol A and hydrogenated bisphenol, and their addition of alkylene oxides Phenolic glycols of the product, alicyclics such as monocyclic or polycyclic diols, and aromatic diols, triols such as glycerin and trimethylolpropane, and the like. These can be used alone or in admixture of two or more.

  A desired polyester resin can be obtained by polycondensation of the above polybasic acid and polyhydric alcohol. A conventionally known polycondensation method can be used as the polycondensation method. Although it varies depending on the type of raw material monomer, it is generally carried out at a temperature of about 150 ° C to 300 ° C.

  Moreover, it can carry out on arbitrary conditions, such as using inert gas as atmospheric gas, using various solvents, or making the reaction container internal pressure normal pressure or pressure reduction. An esterification catalyst may be used to promote the reaction. As the esterification catalyst, metal organic compounds such as tetrabutyl zirconate, zirconium naphthenate, tetrabutyl titanate, tetraoctyl titanate, 3/1 stannous oxalate / sodium acetate, etc. can be used, but they are products. Those that do not color the ester are preferred. Moreover, you may use an alkyl phosphate, an allyl phosphate, etc. as a catalyst or a hue regulator.

In order to control the molecular weight of the product polyester resin, the polymerization temperature, reaction system pressure, reaction time, etc. may be adjusted. The acid value can be controlled by the molar ratio of the carboxylic acid to be reacted and the alcohol, the molecular weight of the polymer, and the like. The molecular weight is preferably a weight average molecular weight (Mw) of 3000 to 100,000. If the lower limit is not reached, the storage property is deteriorated, and if the upper limit is exceeded, melting by heat becomes difficult.

  The acid value of the polyester resin is preferably 20 mgKOH / g or more. More preferably, it is 20-80 mgKOH / g. This is because a polyester resin having an acid value of 20 mgKOH / g or more can improve storage stability and fixability when used with a polymer dispersant having a pyrrolidone group.

As the colorant used in the developer of the present invention, known pigments and dyes can be used.
Specifically, furnace black, lamp black, acetylene black, channel black, C.I. I. Pigment Black, Orthoaniline Black, Toluidine Orange, Permanent Carmine FB, First Yellow AAA, Disazo Orange PMP, Lake Red C, Brilliant Carmine 6B, Phthalocyanine Blue, Quinacridone Red, C.I. I. Pigment blue, C.I. I. Pigment Red, C.I. I. Pigment Yellow, Dioxane Violet, Pictoria Pure Blue, Alkali Blue Toner, Alkali Blue R Toner, First Yellow 10G, Ortho Nitroaniline Orange, Toluidine Red, Barium Red 2B, Calcium Red 2B, Pigment Scar Red 3B Lake, Anthosine 3B Lake, Rhodamine 6B lake, methyl violet lake, basic blue 6B lake, first sky blue, reflex blue G, brilliant green lake, phthalocyanine green G, bitumen, ultramarine blue, iron oxide powder, zinc white, calcium carbonate, clay, barium sulfate, alumina Examples thereof include white, aluminum powder, daylight fluorescent pigment, and pearl pigment.

  In order to improve the dispersibility of the colorant, a colorant having a functional group such as a carboxyl group, a sulfonic acid group, a hydroxyl group, an amino group, or an amide group on the surface by surface treatment or surface modification can be used. .

  The blending amount of the colorant is 3 to 50 parts by weight, preferably 5 to 30 parts by weight with respect to 100 parts by weight of the binder resin. This is because if it is less than 3 parts by weight, the desired concentration cannot be obtained, and if it exceeds 50 parts by weight, the dispersibility and fixability in the binder resin may be impaired.

(Polymer dispersant)
It is preferable to use a polymer dispersant having a pyrrolidone group. Examples thereof include a homopolymer of N-vinylpyrrolidone and a copolymer with (meth) acrylic acid ester, and polyvinylpyrrolidone is preferred.

  The polymer dispersant can be added in an amount of 0.5 to 100 parts by weight, more preferably 1 to 20 parts by weight, based on 100 parts by weight of the toner particles. When the amount is less than 0.5 part by weight, the dispersibility is lowered. When the amount is more than 100 parts by weight, the carrier liquid easily penetrates into the toner particles and the fixability is lowered.

(Metal soap)
The metal soap includes a metal soap represented by the general formula (RCOO) ₂ M (R represents a substituted or unsubstituted alkyl group, alkenyl group, aralkyl group or aryl group, and M represents a divalent metal). Can be used. Two Rs may be the same or different. R may be a straight chain, branched chain or cyclic structure. Preferably, octylic acid, lauric acid, myristic acid, myristic acid, palmitic acid, isopalmitic acid, palmitoleic acid, stearic acid, behenic acid, lignoceric acid, serotic acid, montanic acid, isostearic acid, oleic acid, arachic acid, Single fatty acids such as ricinoleic acid, linolenic acid, behenic acid and erucic acid, saturated fatty acids having 4 or more carbon atoms such as beef tallow fatty acid, soybean oil fatty acid and coconut oil fatty acid, and alkaline earth such as Ca, Ba and Mg Examples thereof include salts with bivalent metals such as a similar metal, Ti, Zn, Cu, Mn, Zr, Pb, Co, and Fe. These may be used alone or in combination of two or more. More preferably, it is a salt of a saturated fatty acid or unsaturated fatty acid having 5 to 15 carbon atoms and the above metal. Further, a salt of octylic acid and the above metal is preferable, and calcium octylate is more preferable.

  The addition amount of the metal soap is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the toner particles. If the amount is below the lower limit, the cleaning property is lowered, and if the upper limit is exceeded, the chargeability is deteriorated.

(Manufacture of developer)
A colored kneaded material composed of the binder resin and the colorant is coarsely pulverized using a cutter mill, a jet mill or the like, and the colorant is dispersed in a secondary particle size of 50 nm to 1 μm, preferably 50 nm to 300 nm. A coarsely pulverized toner is obtained. The coarsely pulverized toner is further wet pulverized in a carrier liquid containing a polymer dispersant, and the toner particles are finely adjusted until the volume average particle size of the toner particles is about 0.1 to 10 μm, preferably about 0.5 to 5 μm. Grind to obtain a concentrated liquid developer. The concentrated liquid developer thus obtained is subjected to dilution / dispersion treatment to obtain an appropriate concentration with a carrier liquid containing additives such as a charge control agent, if necessary, to obtain a liquid developer.

  The present invention will be specifically described by the following examples, but the present invention is not limited to these examples. In the following examples, “part” means “part by weight” unless otherwise specified, “Mw” means “weight average molecular weight”, and “Mn” means “number average”. "Molecular weight", and "Tg" represents "glass transition temperature".

  In the following examples, Mw and Mn were calculated from the results of gel permeation chromatography, respectively. Gel permeation chromatography is a high performance liquid chromatograph pump TRI ROTAR-V type (manufactured by JASCO Corp.), UV spectroscopic detector UVIDEC-100-V type (manufactured by JASCO Corp.), 50 cm long column Shodex GPC A- 803 (manufactured by Showa Denko KK) was used, and the molecular weight of the test sample was determined as Mw and Mn in terms of polystyrene from the chromatographic results. The test sample used was 0.05 g of binder resin dissolved in 20 ml of tetrahydrofuran (THF).

  Tg was measured using a differential scanning calorimeter DSC-20 (manufactured by Seiko Denshi Kogyo Co., Ltd.) under the conditions of a sample amount of 35 mg and a heating rate of 10 ° C./min. The acid value was measured based on JIS K5400 method.

(Manufacture of polyester resin)
Production Example 1
1600 parts of propylene oxide adduct of bisphenol A, 790 parts of terephthalic acid, 100 parts of trimellitic acid in a round bottom flask equipped with a reflux condenser, water / alcohol separator, nitrogen gas inlet tube, thermometer and stirrer Then, nitrogen gas was introduced with stirring, and dehydration polycondensation or dealcoholization polycondensation was performed at a temperature of 200 to 240 ° C. When the acid value of the produced polyester resin or the viscosity of the reaction solution reached a predetermined value, the temperature of the reaction system was lowered to 100 ° C. or less to stop polycondensation. Thus, a thermoplastic polyester resin A was obtained.

  The obtained polyester resin A had Mw = 7000, Mn = 2200, Tg = 68.3 ° C., and acid value = 27.0 mgKOH / g.

Production Example 2
1600 parts of propylene oxide adduct of bisphenol A, 320 parts of bisphenol A ethylene oxide adduct and terephthalic acid in a round bottom flask equipped with a reflux condenser, water / alcohol separator, nitrogen gas inlet tube, thermometer and stirrer 790 parts and trimellitic acid 200 parts were added, nitrogen gas was introduced while stirring, and dehydration polycondensation or dealcoholization polycondensation was performed at a temperature of 200 to 240 ° C. When the acid value of the produced polyester resin or the viscosity of the reaction solution reached a predetermined value, the temperature of the reaction system was lowered to 100 ° C. or less to stop polycondensation. Thus, a thermoplastic polyester resin B was obtained.

  The obtained polyester resin B had Mw = 12000, Mn = 3200, Tg = 78.3 ° C., and acid value = 47.0 mgKOH / g.

(Manufacture of developer)
Example 1
100 parts by weight of polyester resin A and 15 parts by weight of copper phthalocyanine were mixed, thoroughly mixed with a Henschel mixer, melt-mixed with a twin-screw extrusion kneader, cooled, and then coarsely pulverized. Then, it was finely pulverized by a jet pulverizer to obtain toner particles having an average particle diameter of 6 μm.

  1 part by weight of V-216 (manufactured by ISP, polyvinylpyrrolidone) as a polymer dispersant, 0.2 part by weight of calcium octylate (metal soap having an alkyl group having 8 carbon atoms) as a polymer dispersant in 25 parts by weight of the toner particles 75 parts by weight of liquid paraffin (flash point 200 ° C.) and 100 parts by weight of zirconia beads were mixed and stirred for 120 hours in a sand mill to obtain a developer. The average particle size of the toner particles in the developer was 2.6 μm.

Example 2
100 parts by weight of polyester resin B and 10 parts by weight of carbon black (MA-100, manufactured by Mitsubishi Kasei Co., Ltd.) are mixed, mixed thoroughly with a Henschel mixer, melt-mixed with a twin screw extruder kneader, cooled, and then coarsely pulverized did. Then, it was finely pulverized by a jet pulverizer to obtain toner particles having an average particle diameter of 6 μm.

  25 parts by weight of the toner particles, 2 parts by weight of V-220 (manufactured by ISP) as a polymer dispersant, 0.5 part by weight of Diccate Ca (synthetic fatty acid calcium soap having an alkyl group having 10 carbon atoms), fluidized 75 parts by weight of paraffin (flash point 200 ° C.) and 100 parts by weight of zirconia beads were mixed and stirred for 120 hours in a sand mill to obtain a developer. The average particle size of the toner particles in the developer was 2.9 μm.

Example 3
100 parts by weight of polyester resin B and 20 parts by weight of quinacridone were mixed, sufficiently mixed with a Henschel mixer, melt-mixed with a twin-screw extrusion kneader, cooled, and then coarsely pulverized. By finely pulverizing with a jet pulverizer, toner particles having an average particle diameter of 6 μm were obtained.

  25 parts by weight of the toner particles, 6 parts by weight of V-216 as a polymer dispersant, 75 parts by weight of liquid paraffin (flash point 140 ° C.), calcium naphthenate (calcium soap having an alkyl group having 8 to 22 carbon atoms) ) And 100 parts by weight of zirconia beads were mixed and stirred in a sand mill for 120 hours to obtain a developer. The average particle size of the toner particles in the developer was 3.1 μm.

Example 4
The same procedure as in Example 1 was performed except that cobalt octylate was used instead of calcium naphthenate. The average particle size of the toner particles in the obtained developer was 2.6 μm.

Example 5
The same procedure as in Example 1 was performed except that zinc stearate was used instead of calcium naphthenate. The average particle size of the toner particles in the obtained developer was 2.7 μm.

Comparative Example 1
The same procedure as in Example 1 was performed except that the polymer dispersant V-216 was not added. The average particle size of the toner particles in the obtained developer was 7.3 μm.

Comparative Example 2
The same procedure as in Example 1 was performed except that calcium naphthenate was not added.

Comparative Example 3
The same procedure as in Example 1 was performed except that 10 parts by weight of polyesteramine-based Solpers S13940 (Avisia) was used as the polymer dispersant in place of 1 part by weight of V-216.

Comparative Example 4
The same procedure as in Example 1 was carried out except that 1 part by weight of polyesteramine-based Solpers S13940 (manufactured by Avicia) was used as the polymer dispersant in place of 1 part by weight of V-216.

  About the manufactured said developer, the fixing property and the heat-resistant storage stability were evaluated by conducting a real-photo test using the experimental machine of the wet image forming apparatus.

  FIG. 1 is a schematic diagram illustrating an example of a configuration of an experimental machine of a wet image forming apparatus. Around the drum-shaped image carrier 201, a charging device 203, an exposure device 204, a developing roller 103, an intermediate transfer member 301, and an image carrier cleaning blade 204 are arranged in order in the rotation direction indicated by the arrows. Around the transfer body 301, a primary transfer roller 302, a belt conveyance roller 305, a counter roller 306, a secondary transfer roller 307, and a tension roller 308 are disposed.

  The surface of the image carrier 201 is uniformly charged to a predetermined surface potential by the charging device 203, and then image information is exposed by the exposure device 204 to form an electrostatic latent image on the surface of the image carrier 201. . Next, the electrostatic latent image on the image carrier 201 is developed by a developing roller 103 in a developing tank 100 containing a developer 102 containing toner particles and a carrier liquid, and a toner image is formed on the surface of the image carrier 201. . At this time, not only the toner particles but also the carrier liquid adheres to the surface of the image carrier 201. Note that the developer coating layer on the surface of the developing roller 103 is held at a constant thickness by the regulating blade 101.

  Next, the toner image on the image carrier 201 is transferred to the intermediate transfer member 301 by applying a predetermined voltage to 302. A voltage having a polarity opposite to that of the toner particles is applied to 302. At this time, the potential difference from the image carrier is 300 V to 3 kV.

As the intermediate transfer member 301, the belt shown in FIG. 1 or the roller shown in FIG. 2 can be used.
When the intermediate transfer member is a belt, the belt material is a resin or an elastic member, and an elastic member is preferable in view of transferability to rough paper, and one having heat resistance is preferable. The thickness is preferably 50 μm to 1 mm, the volume resistivity is 10 ⁶ to 10 ¹² Ωcm, and the surface resistivity is preferably 10 ⁶ to 10 ¹² Ω / □. Examples of the resin include polyester, polypropylene, polyamide, polyimide, fluorine-based resin, polyphenyl sulfate, and the like, and examples of the elastic body include silicon rubber, fluorine rubber, EPDM, urethane rubber, and nitrile rubber, but are not limited thereto. Considering the stability of conveyance, a multilayer belt having an elastic body on a resin substrate is desirable. In this case, the thickness of the resin substrate is desirably 50 to 200 μm, and the thickness of the elastic body is desirably 200 μm to 1 mm. Further, the outermost layer preferably has a high releasability. Therefore, the surface layer is provided with a hard layer having a thickness of 1 μm or less by using a low surface energy polymer such as fluorine or silicon or by plasma treatment or the like. It is preferable.

  The developer transferred to the intermediate transfer member is transferred to the print medium at the secondary transfer portion (306, 307). A voltage having a polarity opposite to that of the toner is applied to 307. Reference numerals 309 and 310 denote heat rollers on which toner is fixed.

(Storage stability evaluation)
The developer was put in a glass bottle, stored at 50 ° C. for 24 hours, and the particle size before and after storage was measured using SALD-2200 manufactured by Shimadzu Corporation. A particle size change rate (average particle size after storage / particle size before storage) of 1.2 or less was rated as ○, and those exceeding 1.2 were rated as x.

(Fixability evaluation)
The developer to be evaluated was placed in the developing tank 102, and the solid image was developed and the transfer conditions were adjusted so that the toner amount on the medium was 3 g / m ² . An image sample was obtained under the conditions that the system speed was 180 mm / sec, the temperature of the heat roller was 180 ° C., and the NIP passage time was 40 msec.

  Fixability was evaluated by a tape peel test (tape; 3M mending tape), and the density of the peeled tape was measured to determine the fixability. The reflection density before and after tape peeling is measured using an X-Rite densitometer. The density ratio before and after the tape is 95% or more, ◎, 90% or more and less than 95% is ○, and less than 90%. X.

(Cleanability evaluation)
When a developer thin layer of 10 g / m ^{2 is} formed on the developing roller 103 and the urethane rubber cleaning blade 101 is pressed at 20 N / m, the cleaning property is visually evaluated. The case where there was no cleaning residue was marked as ◯.

  As described above, according to the present invention, it is possible to provide a wet developer that achieves both storage stability and fixability and is excellent in cleaning properties.

It is a schematic diagram which shows an example of a structure of a wet image forming apparatus. It is a schematic diagram which shows another example of a structure of a wet image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Developing tank 101 Control blade 102 Developer solution 103 Developing roller 201 Image carrier 202 Cleaning blade 203 Charging device 204 Exposure device 301 Intermediate transfer body 302 Primary transfer roller 305 Belt transport roller 306 Opposed roller 307 Secondary transfer roller 308 Tension roller 309 Heat roller 310 Heat roller

Claims (3)

A wet developer in which toner particles comprising at least a colorant and a binder resin are dispersed in a non-volatile carrier liquid using a polymer dispersant,
The polymer dispersant has a pyrrolidone group, and the carrier liquid has a general formula (RCOO) ₂ M (R represents a substituted or unsubstituted alkyl group, alkenyl group, aralkyl group or aryl group, and M represents a divalent group. A wet developer containing a metal soap represented by a metal).   The wet developer according to claim 1, wherein the metal soap is a metal salt of a fatty acid having 5 to 15 carbon atoms.   The wet developer according to claim 1 or 2, wherein the binder resin is a polyester resin having an acid value of 20 mgKOH / g or more.

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